Squeegees for screen and stencil printing



July 10, 1956 J. GROAK SQUEEGEES FOR SCREEN AND STENCIL PRINTING Filed June 5, 1952 6 Sheets-Sheet 2 July 10, 1956 J. GROAK SQUEEIGEES FOR SCREEN AND STENCIL PRINTING Filed June 3, 1952 6 Sheets-Sheet 3 July 10, 1956 J. GROAK SQUEEJGEEIS FOR SCREEN AND STENCIL PRINTING Filed June 3, 1952 6 Sheets-Sheet 4 I 4 WW I r v 33 wad/( July 10, 1956 J. GROAK SQUEEGEES FOR SCREEN AND STENCIL PRINTING Filed June a. 1952 6 Sheets-Sheet 5 July 10, 1956 J. GROAK 2,753,794

SQUEEGEES FOR SCREEN AND STENCIL PRINTING Filed June 5, 1952 6 Sheets-Sheet 6 J 1 I '3 3' a 0: v g as L: 3 E \w: I I i'g I i w izl/a/ffi f E a/$1 000? iM /ZQ I AWE n74 United States Patent SQUEEGEES FOR SCREEg AND STENCIL PRIN TIN Josef Groak, London, England, assig-nor to Chambon Limited, London, England This invention relates to machines for screen and/or stencil printing, in which an ink in the form of printing ink, paint, enamel, lacquer, adhesive or the like, is squeezed or pressed by means of a squeegee through the apertures of a meshed screen or a stencil or a screen and stencil together onto a receiving surface to be printed on. For simplicity the expression perforate mask will be used hereinafter whenever it is intended to refer in a generic sense to such screen or stencil or combination of screen and stencil.

In the operation of screen and/or stencil printing machines, for example, of the silk screen type, it is customary to provide a squeegee having a smooth, usually resilient, surface, for example, a rubber blade, for forcing the ink through the apertures of the perforate mask. However, the squeegees hitherto used do not allow very much control over the flow of ink to the work.

An object of the present invention is to provide an improved machine for screen and/or stencil printing, in

which the operation and nature of the squeegee are such as to enable greater control to be exercised over the flow of ink through the perforate mask than has been possible hitherto.

It is to be understood that the term ink is used herein as a generic term to include not only the liquid or semi-liquid materials referred to above, but also liquid or semi-liquid compositions comprising thermoplastic materials solid at ordinary temperatures, but used in the molten state, or comprising materials capable of setting by hardening with the application of heat or at ordinary temperature. Such thermoplastic or setting compositions can be used for printing in relief.

The machine of this invention, comprises a frame for holding a perforate mask, a squeegee adapted by contact with the mask to feed ink therethrough and having in its contact surface ink-carrying recesses, and means for causing relative movement between the contacting surfaces of the squeegee and mask in a direction transversely of the recesses so that the squeegee exerts a wiping action on the surface of the mask and forces the ink through the mask onto the surface to be printed on.

The surface of the squeegee may be flat or curved. In the case of a squeegee having a curved surface, the relative movement between the contacting surfaces of the squeegee and mask is caused at least in part by rotating the curved surface of the squeegee in contact with the mask. Such a squeegee may be in the form of a roller or segment, or it may comprise a fiat endless band passing round guide rollers, preferably in such manner as to present a curved surface to the perforate mask. In some cases a flat disc-shaped squeegee may be used, which is revolved with its flat surface in contact with the perforate mask. The squeegee may be built up of a number of flat blades mounted radially on a shaft or drum, the outer edges of the blades forming the surface of the squeegee and the spaces between them forming the ink-carrying recesses.

ice

The ink-carrying recesses may take the form of straight or zi-g-zag grooves in the surface of the squeegee extending transversely to the direction of relative movement between the contacting surfaces of the squeegee and perforate mask. In the case of roller or segmental squeegees the transverse grooves may be longitudinal or helical. -Al 'ternatively the recesses maybe of other configuration, for example, they may be indentations of any desired shape, for example, of square, circular or L-shape.

The relative movement between the contacting surfaces of the squeegee and perforate mask may be caused by maintaining one of those surfaces stationary and moving the other surface, or by moving both surfaces in opposite directions or in the same direction at difier'ent speeds. In the case of a squeegee having a curved surface, such as as roller, it is preferable that the contacting surface of the squeegee should move in a direction opposite to that in which it would move if it rolled normally on the surface of the perforate mask. Thus, for example, if the perforate .mask is moved past a stationary squeegee roller, the roller should preferably rotate so that the surface thereof in contact with the mask moves in a direction opposite to that of the mask.

The machine of this invention may be used for printing on sheet material, such as paper, cardboard, fabric, foils of synthetic plastics, rubber, metal or laminated materials, either in the form of separate sheets or continuous webs, and it may also be used for printing materials or objects of other shape, for example, ceramic articles, glass bottles or boxes.

The new machine is especially suitable for producing prints in relief, for example, for printing braille literature, with a viscous liquid ink capable of setting to a solid state, and with the use of a stencil of a thickness, for example, 0.012 inch, appropriate for producing printed portions of a desired height. As such inks there may be used those Containing thermoplastic materials, which are applied in the molten state and solidify on cooling, or inks containing thermosetting materials which are hardened .by the subsequent application of heat.

In the case of a roller squeegee the ink may be supplied thereto directly by rotating it with part of its sur-w face in contact with or immersed in ink contained in a trough, or by means of an inking roller rotating in an ink trough and making contact with the surface of the squee gee roller. In both cases surplus ink may be removed from the squeegee roller by means of a doctor blade or roller bearing against a part of its surface in advance of the printing position. Alternatively, the bottoms of the grooves or other recesses in the squeegee roller may communicate through duets with the interior of the roller, ink-delivery means, for example, a channel or row of channels, is located within the roller in alignment with the printing position for supplying ink through the ducts to the recesses in turn as they reach the printing position, and means is provided for feeding ink under pressure to the ink-delivery means. Thus, the squeegee may take the form of a hollow roller rotating as a close fitting sleeve upon a fixed cylindrical hollow core having in its Wall behind the printing position the aforesaid channel or row of channels which register with the squeegee ducts in turn as the squeegee rotates. This method of feeding the ink is especially suitable when printing with viscous inks, for example, thermoplastic or thermosetting compositions.

The flow of ink to the work may be controlled by varying the pressure with which the squeegee is urged against the surface of the perforate mask or by varying the difference in speed between the surfaces of the squeegee and the screen, an increase in pressure or an increase in the difference in speed increasing the flow of ink to the work. The flow of ink is also to some extent governed by the depth of the recesses and their width in the direction of relative movement between the surfaces of the squeegee and mask, an increase in the depth or width increasing the flow of ink.

The depth and width of the recesses is governed mainly by the viscosity of the ink used, the depth or width being smaller with inks of lower viscosity and greater with inks of higher viscosity.

In contradistinction to the hitherto usual forms of squeegee, the squeegee used in the present invention, owing to its enhanced capacity for retaining ink, may be arranged in any convenient position with respect to the perforate mask. For example, the squeegee may be positioned above or at one side of the mask. Alternatively, the work to be printed on, such as paper or other material, may be above the mask with the squeegee positioned beneath the mask. This position of the squeegee is especially advantageous when working with low viscosity liquid inks.

The printing machine is advantageously constructed as a rotary machine comprising a rotary drum frame for holding a perforate mask, a squeegee roller mounted within the drum frame for rotation in contact with the inner surface .of the mask at the printing position, means for rotating the drum frame and for rotating the squeegee roller at speeds such as to cause relative movement between the contacting surfaces of the roller and mask as hereinbefore described, and means for guiding material to be printed on in contact with the outer surface of the mask at the printing position. Preferably the contacting surfaces of the roller and mask are moved in opposite directions.

In order to print in one operation on both sides of the material for example, a continuous web of paper, two drum frame and squeegee roller assemblies may be arranged one on each side of the path of the material. These two assemblies may be arranged opposite one another with their axes on a line at right angles to the path of the material, and at least one of the assemblies is urged towards the other so that the outer surfaces of their perforate masks during printing bear against the surfaces of the material in the printing position. Alternatively, the two assemblies may be spaced apart along the path of the material so as to print upon opposite sides thereof,

and a pressure roller may be provided opposite to the printing position of each drum frame to urge the material against the perforate mask. The material may in either case be guided in the form of a continuous web towards and away from the printing position or positions. When 'the assemblies are arranged opposite to one another and the squeegee rollers have ink-carrying grooves therein, it is preferable that the grooves in the opposing surfaces of the rollers at the printing position should be at an angle to one another, so as to avoid the tendency which grooves extending parallel to the axes of the rollers might have of intermeshing with one another, especially if the perforate masks tend to flex under the pressure exerted by the rollers. Rotary machines of this kind are especially suitable for printing in relief as described above.

Alternatively, a screen and/ or stencil printing machine in accordance with the invention may be constructed in the form of a flat-bed machine comprising a flat frame for holding a perforate mask, a squeegee roller mounted for rotation in contact with the surface of the mask, and means for causing relative movement between the frame and squeegee roller and for rotating the roller in a direction transversely of its recesses for the purpose described above. The mask-holding frame may be stationary and the squeegee roller moved relatively thereto, but preferably the roller is stationary and the frame is moved. Advantageously, the squeegee roller is located beneath the mask-holding frame, and the material to be printed on is supported against the upper surface of the mask.

Machines constructed in accordance with the invention are also readily adapted for use in making small articles such as pellets, granules, buttons and other articles of any desired shape by forcing, for example, thermoplastic material in its softened state through appropriately shaped apertures in stencil plates of the requisite thickness on to receiving surfaces from which the deposited material can readily be detached on cooling. For example thin squares, diamonds, circles or stars for decorative purposes can be made by forcing a softened thermoplastic composition through appropriately shaped apertures on to a chromium plated surface from which the articles can be removed on hardening.

Examples of the method and apparatus of the invention will now be described with reference to the accompanying drawings in which Figures 14 show various forms of squeegees constructed in accordance with the invention,

Figure 5 is a side elevation of a rotary screen and/ or stencil printing machine constructed in accordance with the invention,

Figre 6 is a cross-sectional elevation through the drum frame and squeegee roller assemblies of the machine shown in Figure 5,

Figure 7 is a plan view partially in section of the drum frame and squeegee roller assembly shown on the left in Figure 5 Figure 8 shows a modified form of ink delivery means for use in the machine shown in Figures 5-7,

Figure 9 is a side elevation of a flat-bed screen and/ or stencil printing machine constructed in accordance with the invention, and

Figure 10 is a cross-sectional elevation through the paper-carrying roller, perforate mask and squeegee roller of the machine shown in Figure 9.

Figure 1 shows an example of a squeegee roller consisting of a core 1 having upon it a covering of resilient material 2, such as rubber. The surface of the resilient covering is formed with grooves 3 extending parallel with the axis of the roller. The tops of the ribs 4 between the grooves constitute the surface of the roller which wipes the perforate mask. The grooves are shown as extending parallel to the axis of the roller, but they may, if desired, extend helically at a small angle to the axis of the roller. In Figure 2 is shown a squeegee consisting of an endless band 5 of resilient material passing round two guide rollers 6 and 7. The endless band has grooves in its surface similar to those shown in Figure 1. Preferably one of the curved portions of the band passing over a guide roller would move in contact with a perforate mask to force ink therethrough.

Figure 3 shows a flat squeegee having in its surface sinuous grooves 8, and Figure 4 shows a similar squeegee having L-shaped recesses 9 in its surface. It will be understood that grooves and recesses such as are shown in Figures 3 and 4 could also be formed in the surface of a roller squeegee.

In Figures 5, 6 and 7 is shown a rotary screen and/or stencil printing machine. As shown, the machine is provided with stencils suitable for printing in relief, especially for printing braille literature, but it could also be used for ordinary screen and/ or stencil printing. This machine has two drum frames 10 and 11 mounted opposite to one another with their axes on a line at right angles to the path of a web of paper 12 passing between them. The machine is driven by an electric motor 13 mounted in the frame 14 of the machine, and the motor drives a shaft 15 through pulleys 16 and 17 and a belt 18. On the shaft 15 are two worm gears 19 and 20, one of which has a right-hand thread and the other a left-hand thread, and which worm gears drive pinions fixed to shafts 21 and 22, respectively. One of these pinions 23, namely that on the shaft 21, is shown in Figure 7. Also fixed to the shafts 21 and 22 are toothed pinions 24 and 25 which drive large toothed wheels 26 and 27 through chains 28 and 29, respectively. The toothed wheels 26 and 27 are fixed to shafts 30 and 31 on which are also fixed toothed pinions 32 and 33 which drive the drum frames 10 and 11 respectively through chains 34 and 35 engaging toothed wheels integral with the drum frames, one of which wheels 36 is shown in Figure 7. The drum frames are thus rotated in opposite directions as shown by the arrows A and B.

Each drum frame is built up of two end plates secured together by spacing rods and fixed to a hollow shaft. Thus, for example, as shown in Figure 7, the left-hand drum frame shown in Figure 5 is built up of two end plates one of which is shown at 37, the end .plates being rotatable on a fixed hollow shaft 38. The end plates are secured together at diametrically opposite parts of their periphery by means of tie rods 39 secured to projecting portions 40 of the end plates. Each drum frame carries two stencil plates 41 of thin metal or plastic. Each stencil is secured at one end to the plates by means of holding devices 42 and is maintained under tension against the flanges of the end plates, for example, the flange 37a of the end plate 37, by means of spring-loaded gripping members 43 pivoted to the end plates.

The hollow shaft 38 is fixedly mounted at each end in bearing blocks one of which is shown at 44 in Figs. 5 and 7, and the ends of the inner shaft 21 are rotatably mounted in those blocks. The bearing blocks are slidably mounted in housing blocks one of which is shown at 45. Each housing block 45 has a pin 46 which carries a roller 47 running in a cam groove 48 formed in the outer side of the adjacent end plate, for example, 37, of the drum frame. The cam groove has two diametrically opposed portions of its track bulging radially outwards so that during the rotation of the drum frame the cam groove moves the drum frame to the left, as seen in Figure 7, momentarily at each half revolution, the drum frame carrying with it the hollow shaft 38 and the bearing block 44. Thus, while the cam grooves urge the opposing stencils under pressure into contact with the intervening paper web 12 during a printing operation, they momentarily force the drum frames apart during those portions of a revolution in which the gaps between adjacent stencils pass the printing position. While the drum frames are held apart the paper web is released and its feed is thereby momentarily interrupted.

In order to enable the drum frames to be spaced apart at will by hand for any reason, for example, to interrupt a printing operation, levers 49 (only one of which is shown) are connected to the housing blocks 45 of the left hand drum frame 10. The levers 49 are moved lengthwise by means of eccentrics 50 fixed to a cross shaft 51 rotated by a hand crank 52.

As shown in Fig. 6 there is mounted within each drum frame a squeegee roller 53. This roller and its associated parts are shown in section in the drum frame 11, and the driving mechanism therefor is shown in side elevation in the drum frame 10. The squeegee rollers consist of a core provided with an outer covering of rubber the surface of which is grooved, for example, as shown in Fig. 1. However, the grooves are set at an angle to the roller axis so that the opposing ribs and grooves cannot inter-mesh for the reason hereinbefore explained.

Each squeegee roller 53 is supplied with ink by means of an inking .roller 54 dipping within ink contained in a trough 55. Surplus ink is removed from the surface of the squeegee roller by means of a doctor roller 56, and a rigid metal doctor blade 57 removes surplus ink from the doctor roller. The doctor blade 57 is fixed to a bar 58 movably mounted at the top of the rear wall 59 of the ink trough. The bar 58 is engaged by the flange 60 on an adjusting screw 61 for the purpose of adjusting the doctor blade relatively to the doctor roller. Three or four such adjusting screws are provided at intervals along the bar 58, although only one is shown.

The ink trough 55 together with the squeegee roller and associated rollers are carried at each end by brackets 62, only one of which is shown. Each bracket 62 is -'6 secured by means of a bolt 64 upon :an accentric 63 rdtatable on the hollow shaft 38. By rotating the eccen tries the brackets are moved forwardly o-r rearwardly to vary the pressure of the squeegee roller upon the inner surface of its stencil.

The squeegee rollers 53 are driven from the respective shafts 21 and 22. Thus, the shaft 21 carries a gear Wheel 65 which drives in turn the gear wheels 66 and 67. An opening is formed in the wall of the hollow shaft 38 to permit the wheel 66 to mesh with the wheel 65 within the hollow shaft. Coaxial with the gear wheel 67 is a toothed wheel 68 which drives a toothed wheel 69 through a chain 70. Coaxial with the toothed wheel 69 is a gear wheel 71 which drives a gear Wheel 72 fixed to the axis of the squeegee roller 53. The doctor roller 56 is also driven by the gear wheel 71 which meshes with a gear wheel (not shown) fixed to the axis of the roller 56. The inking roller 54 is driven by the gear Wheel 71 through an idler gear wheel (not shown) so that the roller 54 rotates in a direction opposite to that of the rollers 53 and 56. The directions of rotation of these rollers are shown by arrows in Fig. 6. Thus, each squeegee roller rotates in a direction opposite to that of the stencils successively co-operating therewith, so that the surface of the squeegee roller contacting the inner surface of a stencil at the printing position moves downwardly, i. e. in a direction opposite to that of the inner surface of a stencil.

A thermosetting ink is used, for example, one containi ng a urea-formaldehyde condensation product and a hardening accelerator therefor, and is forced through the holes in the stencil-s simultaneously on to opposite sides of the paper web 12 at the printing position. Owing to the thickness of the stencils raised printed portions are left on the surface of the paper web as it moves upwardly out of contact with the stencils. The Web then passes through a heating device 73 in which the raised printed portions are hardened by heat to the solid state. Each pair of opposing stencils prints two pages of braille writing, one on each side of the same length of web. The paper web is drawn from a roll 74 over a roller 75 into the printing position, and is then guided over rollers 76 through the heating device 73 and finally between a pair of feeding rollers 79. The web is subsequently cut into lengths suitable for being made up into books.

In Fig. 8 is shown diagrammatically an alternative form of ink delivery means, which can be used in place of the ink trough assemblies shown in Figs. 5-7. Each squeegee roller 80 is hollow and consists of an inner sleeve 81 of rigid material, such as metal, having thereon a cove-ring 82 of rubber in the surface of which are formed grooves 83. At the bottoms of the grooves are ducts 84 which communicate with the interior of the squeegee roller. The squeegee roller rotates upon a fixed hollow shaft 85 which has in its wall adjacent to the printing position an ink-delivery channel 86 in the form of a horizontal slot. Ink is supplied under pressure to the interior of the shaft 85, and is forced through the channel 86 into the ducts 84 and thence into the grooves 83 in turn as they pass in register with the channel 86 at the printing position.

In Figs. 9 and 10 is shown a flat-bed screen and/or stencil printing machine. In this machine a fiat perforate mask 90 is reciprocated between a grooved squeegee roller 91 and a paper-carrying roller 92. The mask is carried in a frame 93 which is detachably fixed to a reciprocating bed 94. On' the underside of the bed 94 are two toothed racks extending longitudinally one on each side of the bed, and one of which racks 95 is shown in Fig. 9. In the base of the machine are two corresponding toothed racks 96. The bed 94 is reciprocated by means of a crank lever 97 rotated by a shaft 98, a connecting rod 99 and a pair of toothed wheels 100 which mesh with the racks 95 and 96.

As shown in Fig. 10, during a printing operation, the

paper to be printed on is carried by a roller 92 and held thereby in contact with the upper surface of the perforate mask 9! of which the lower surface makes contact with the surface of the squeegee roller 91. The squeegee roller is supplied with ink by an inking roller 101a which dips beneath the surface of the ink in a trough 101. Surplus ink is removed from the squeegee roller by means of a doctor roller 102 which is itself wiped by a doctor blade 193. The squeegee roller, associated rollers and ink trough are all mounted as a single unit at each side on trunnion blocks one of which is shown at 1 34 in Fig. 9.

The paper-carrying roller 92 is similarly mounted at each end in trunnion blocks one of which is shown at 195. The trunnion blocks are connected together by means of links 106 articulated to one another at 107, and are urge towards each other by springs 108. The reciprocating bed 94 has at its ends lugs 109 and 110, which strike the articulated links at the end of each stroke of the bed 94. In the flexed position of the links 106 shown in Fig. 9 the roller 92 and squeegee roller 91 are forced towards each other by the springs 19% into their operative printing position. As shown in Fig. 9, the bed 94 is at one end of its stroke at the beginning of a printing operation. The bed 94 is moved to the right during the printing operation, and at the end of this stroke the lug 109 strikes the links 106 so as to force apart the trunnion blocks 1% and 105 against the action of the springs 198 and move the roller 92 and squeegee roller 91 away from the perforate mask. During the return stroke the mask and squeegee roller are inoperative, and at the end of this stroke the lug 110 strikes the links 106 to flex them and so bring the roller 92 and squeegee roller 91 back to their operative position for the next printing operation.

The paper-carrying roller 92 is provided in its periphery with a row of grippers 111 which operate, in a manner known in printing machines, to grip a paper sheet fed down the table 112, carry the sheet round with the roller past the printing position, and, after the completion of one revolution, release the sheet adjacent to the edge 113 of the paper-receiving table 114. The grippers then revolve idly with the roller during the completion of the printing operation, until they reach the lower edge of the table 112, where they grip a fresh sheet and carry it round past the printing position. While the bed 94 is performing a complete stroke from left to right during a printing operation, the grippers move from the position shown in Fig. and back to that position as the roller performs one revolution, and while the bed 94 performs its complete return stroke the remainder of the printed sheet passes on to the table 114, and the grippers grip a fresh sheet and bring it into the printing position.

This machine is especially suitable for use with an ink of low viscosity.

I claim:

1. A screen and/or stencil printing machine, which comprises a frame for holding a perforate mask, a squeegee adapted by relative movement in contact with the mask to feed ink therethrough and having in its contact surface ink-carrying depressions arranged in succession in the direction of said relative movement, and means for causing relative movement between the contacting surfaces of the squeegee and mask in the direction of the said succession of depressions so that the squeegee exerts a wiping action on the surface of the mask and forces the ink from the said depressions through the mask on to the surface to be printed on.

2. A screen and/or stencil printing machine, which comprises a frame for holding a perforate mask, a squeegee adapted by relative movement in contact with the mask to feed ink therethrough and having a resilient contact surface and in the said surface ink-carrying depressions arranged in succession in the direction of said relative movement, and means for causing relative movement between the contacting surfaces of the squeegee and mask in the direction of the said succession of depressions so that the squeegee exerts a wiping action on the surface of the mask and forces the ink through the mask from the said depression on to the surface to be printed on.

3. A printing machine as claimed in claim 2, wherein the depressions in the contact surface of the squeegee take the form of grooves extending transversely to the direction of the said relative movement.

4. A screen and/or stencil printing machine, which comprises a frame for holding a perforate mask, a squeegee adapted by relative movement in contact with the mask to feed ink therethrough and having a curved contact surface of resilient material and in said surface inkcarrying depressions arranged in succession in the direction of said relative movement, and means for causing relative movement between the contacting surfaces of the squeegee and mask in the direction of said succession of depressions so that the squeegee exerts a wiping action on the surface of the mask and forces the ink from the said depressions through the mask on to the surface to be printed on, the said means including means for rotating the curved surface of the squeegee in contact with the mask.

5. A printing machine as claimed in claim 4, wherein the squeegee takes the form of a roller.

6. A printing machine as claimed in claim 5, wherein means is provided for applying the ink directly to the contact surface of the squeegee roller.

7. A. printing machine as claimed in claim 5, wherein the bottoms of the depressions in the squeegee roller communicate through ducts with the interior of the roller, ink-delivery means is located within the roller in alignment with the printing position for supplying ink through the ducts to the depressions in turn as they reach the printing position, and means is provided for feeding ink under pressure to the ink-delivery means.

8. A printing machine as claimed in claim 5, wherein the squeegee roller has a succession of ink-carrying grooves in its contact surface extending transversely t0 the direction of the said relative movement.

9. A printing machine as claimed in claim 8, wherein the means for causing the said relative movement includes means for rotating the squeegee roller in a direction such that its surface of contact with the mask moves in a direction opposite to that in which it would move if the roller rolled normally on the surface of the mask.

10. A printing machine as claimed in claim 1, wherein the squeegee is positioned beneath the holding frame for the perforate mask, and means is provided for holding the work to be printed on against the upper surface of the mask.

11. A rotary screen and/or stencil printing machine, which comprises a rotary drum frame for holding a perforate mask, a squeegee roller mounted within the drum frame for rotation in contact with the inner surface of the mask at the printing position to feed ink therethrough and having in its contact surface ink-carrying depressions arranged in succession in the direction of said rotation, means for rotating the drum frame and for rotating the squeegee roller at speeds such as to cause relative movement between the contacting surfaces of the squeegee roller and mask in the direction of the said succession of depressions so that the squeegee roller exerts a wiping action on the surface of. the mask and forces ink through the mask, and means for guiding material to be printed on in contact with the outer surface of the mask at the printing position.

12. A rotary printing machine as claimed in claim ll, wherein the contact surface of the squeegee is of resilient material.

13. A rotary printing machine as claimed in claim 12, wherein the depressions in the contact surface of the squeegee roller take the form of a succession of grooves 9 extending transversely to the direction of said relative movement.

14. A rotary screen and/or stencil printing machine, which comprises a rotary drum frame for holding a perforate mask, a squeegee roller mounted within the drum frame for rotation in contact with the inner surface of the mask at the printing position to feed ink therethrough and having in its contact surface ink-carrying depressions arranged in succession in the direction of said rotation, means for rotating the drum frame, means for rotating the squeegee roller in a direction such that its contact surface moves in the direction of said succession of depressions and oppositely to the direction of movement of the surface of the mask so that the squeegee roller exerts a wiping action on the surface of the mask and forces ink through the mask, and means for guiding material to be printed on in contact with the outer surface of the mask at the printing position.

15. A rotary screen and/or stencil printing machine, which comprises two rotary drum frames each adapted to hold a perforate mask, a squeegee roller mounted for rotation in contact with the inner surface of the mask of each drum frame at the printing position to feed ink through the mask and having in its contact surface inkcarrying depressions arranged in succession in the direction of said rotation, means for rotating the drum frames and squeegee rollers at speeds such as to cause relative movement between the contacting surfaces of the squeegee rollers and their respective masks in the direction of the said succession of depressions so that the squeegee rollers exert a wiping action on the surfaces of the masks and force ink therethrough, and means for guiding material to be printed on so that one surface thereof makes contact with the outer surface of a mask at the printing position of one drum frame and squeegee roller assembly and the other surface of the material makes contact with the outer surface of a mask at the printing position of the other drum frame and squeegee roller assembly.

16. A rotary printing machine as claimed in claim 15, wherein the two drum frame and squeegee roller assemblies are arranged with their printing positions opposite to one another and their axes on a line at right angles to the path of the material, and means is provided for urging at least one of the assemblies towards the other so that the outer surfaces of their perforate masks during printing bear against the surfaces of the material in the printing position.

17. A rotary printing machine as claimed in claim 16, wherein the contact surfaces of the squeegee rollers have a succession of transversely extending ink-carrying grooves therein arranged so that the grooves in the opposing surfaces of the rollers at the printing position are at an angle to one another.

18. A rotary printing machine as claimed in claim 15, wherein guiding means is provided for guiding sheet material in the form of a continuous web towards and away from the printing position.

19. A rotary printing machine as claimed in claim 11 and adapted for printing in relief with a viscous liquid ink capable of setting to a solid state, wherein the drum frame carries a stencil of a thickness appropriate to produce printed portions of a desired height.

20. A flat-bed screen and/or stencil printing machine,

which comprises a flat frame for holding a perforate mask, a squeegee roller mounted for rotation in contact with the surface of the mask and having in its contact surface ink-carrying depressions arranged in succession in the direction of said rotation, and means for causing relative movement between the frame and squeegee roller and for rotating the roller in the direction of the said succession of depressions so that the squeegee roller exerts a wiping action on the surface of the mask and forces the ink through the mask on to the surface to be printed on.

21. A flat-bed screen and/or stencil printing machine, which comprises a flat frame for holding a perforate mask, a squeegee roller mounted for rotation in contact with the surface of the mask and having a contact surface of resilient material and a succession of ink-carrying grooves in the said resilient surface extending transversely of the direction of rotation, means for causing relative movement between the frame and the squeegee roller, and means for rotating the squeegee roller in a direction such that the contacting surfaces of the roller and mask move in opposite directions.

22. A fiat-bed printing machine as claimed in claim 21, wherein the squeegee roller is mounted stationarily beneath the mask-holding frame, and means is provided for moving the frame past the roller during a printing operation and for supporting the material to be printed on against the upper surface of the mask during printing.

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